Jay Leno, hosting the Tonight Show last week, asked Dick Clark how he managed to look so young.

Clark, 62, host of American Bandstand, the $100,000 Pyramid and producer of other TV shows, told Leno he just keeps taking vitamins.

Which pleased top executives at Fort Lauderdale-based Sundown Vitamins, because the privately owned company signed up Clark in January to be its national pitchman.

There are still skeptics who consider vitamins to be quack medical remedies, as the opiate of the people. But more scientists and doctors are changing their minds. Vitamins now are being touted as instrumental in fighting everything from cancer and heart disease to old age. And companies such as Sundown are cashing in.

Sundown was founded 18 years ago by Carl DeSantis, a backslapping, muscular guy who was managing a drugstore in Miami Beach at the time. DeSantis decided to earn a few bucks on the side by selling a private-label sunburn lotion, formulated by the store's pharmacist.

He hired a sales staff, and before long he was selling vitamins. Now DeSantis, 52, owns the largest privately owned vitamin company in the United States.

But maybe not for long. DeSantis says he's considering a public offering. Going public would make it easier to raise money for expansion and, with the stock market reaching new highs, the time is right, DeSantis said.

"It's not a one-man band anymore," he said.

Sales last year topped $100 million. Sundown now has more than 700 employees, with 340 in the Broward headquarters, where they will package and distribute roughly 5 billion vitamin tablets this year. The company is negotiating to open a Rexall store in Moscow. Sundown bought Rexall in 1986.

Most of Sundown's products are sold through discount drug stores such as Phar-Mor, Freddy's and Drug Emporium, but the company also owns a mail-order business and a multi-level marketing firm similar to the bigger Amway and Shaklee operations. A New Jersey company, Chem International, makes all of Sundown's products.

In the next few weeks, Sundown will introduce a new multi-vitamin, Formula for Life, with Clark's photo on the box. Clark said he knew and used some of Sundown's vitamins before the company approached him about being its spokesman. "I had used some of their stuff, unbeknownst to them," he said in a phone interview.

Clark said he has managed to stay fit because his mother started him on vitamins when he was 5 years old. "I tell people there is no secret," Clark said. "You just select your parents very carefully."

And you take your vitamins.

Nutritionists all agree that adults can get all the vitamins they need if they just eat lots of vegetables and fruits -- lots and lots of them.

But most adults don't. The National Center for Health Statistics says only 9 percent of adults eat the way they're supposed to.

DeSantis, who takes half a dozen vitamins every morning, got into vitamins by way of finding a better sunburn lotion.

In 1974 he was managing a drugstore at 69th Street and Collins Avenue in Miami Beach. DeSantis noticed that all the tourists were buying Solarcaine. "Sold a ton of it," he recalled. So DeSantis talked to his pharmacist and they came up with the idea for Sundown Sun Burn protectant.

The sunburn lotion did OK, but DeSantis started a vitamin line after watching vitamin sales pick up. He thought the vitamins would generate more money to promote the suntan lotion. But as things worked out, DeSantis eventually sold his suntan lotion.

DeSantis also eventually brought his three children into the company. Sons Damon, 27, and Dean, 30, are top executives, and his oldest child, Debby, 33, just joined the company after spending nine years at Walgreens as a pharmacist.

DeSantis and his executives say the Sundown line is the biggest-selling vitamin brand in the country. "We know that if we're put side by side with those other brands, we'll outsell them every time," said Richard Wisely, director of marketing. "We've never lost in that kind of test."

Maybe so, but a top competitor says his salespeople aren't worried about Sundown. Harvey Kamil, chief financial officer at Nature's Bounty, a New York- based vitamin company, said Sundown is mostly a Florida and Southeast-based company.

"But I don't think they have much presence nationwide, except with Phar- Mor," Kamil said. "If you ask my sales force who their top competitors are, they say Pharmavite and P. Leiner."

How Sundown stacks up against the competition is hard to figure because the company is private and DeSantis won't divulge bottom-line figures. But Sundown and most of its competitors have annual sales in the $100 million range, though Nature's Bounty totaled $73 million last year.

Nature's Bounty earned $1 million last year; P. Leiner earned $5.4 million. Both are public companies. Sundown gave $3 million to charity last year, for Kurd and Iraqi relief. DeSantis scoffs at the idea that Sundown's profits are comparable to his major competitors'.

"Two or three of them together don't make our net profit," he said, though DeSantis declined to be specific.

The bottom line keeps improving, he says, but DeSantis says there are some disadvantages in getting bigger, too.

"I used to deal with labels and formulas, real fun stuff," DeSantis said. "Now I've got to look at books all the time."